Method of coating with a coal extract and baking



Patented Oct. 6, 1953 METHOD OF COATING WITH A COAL EXTRACT AND BAKING Ian Gordon Cumming Dryden, London, England application June 28, 1949, Divided and this applica- 50, Serial No. 202,825. In Great Britain February 12, 1948 No Drawing. Original Serial No. 101,911. tion November 6, 19

17 Claims. 1

The present invention relates to improvements in Method of Coating With a Coal Extract and Baking, and is a division of my prior copending application Serial No. 101,911, filed June 28, 1949, entitled Production and Use of Coal Extracts and Solutions Thereof, and now abandoned.

It is known that bituminous coals can be treated with organic substances having a solvent action thereon, whereby a part of the coal substance is dissolved to give a colloidal or molecular solution. Complete dissolution of the coal has not been attained without the assistance of chemical reaction. Such solvents can be divided broadly into two groups: Those which will dissolve useful quantities of material only at elevated temperatures and pressures, and those which cause considerable swelling, peptisation or dissolution at temperatures at and below the boiling point of the solvent.

An object of the present invention is to provide a process for producing solutions of coal extracts with the aid of new and improved solvents of the latter type, which enable bituminous coals to be extracted under a wide variety of moderate conditions, and enable a considerable degree of extraction to be obtained with certain coals. Some of these new solvents enable stable aqueous dispersions of the soluble material to be prepared.

According to this invention, coal extract solutions are made by treating bituminous coal with a liquid aliphatic or araliphatic amine, which contains at least one primary amine group, and of which the viscosity at the temperature of the treatment is not greater than 30 centipoises, under atmospheric pressure and at a temperature at or below the boiling point of the amine to form a solution of a part of the coal, and the solution is separated from the insoluble material.

The expression araliphatic amine is used herein and in the appended claims to denote an amine in which a primary amino group is attached to the aliphatic portion of a residue which is partly aromatic and partly aliphatic. As suitable aliphatic or araliphatic amines there may be mentioned: Primary aliphatic monamines containing not more than 12 carbon atoms, for example, n-propylamine, isopropylamine, amethyl-propylamine, n-amylamine, n-dodecylamine, allylamine or monoethanolamine; alkylene diamines containing not more than 6 carbon atoms in the aliphatic chain, for example, ethylene diamine, propylene diamine r hexamethylene diamine; polyalkylene polyamines containing at least one primary amino group, for example, diethylene triamine; and araliphatic amines, for example, benzylamine or p-phenylethylamine.

The proportion of material which can be extracted from the coal depends on the rank of the coal treated, on the temperature and time of the treatment, and to a smaller extent on the type of amine used. Good extractions are obtained with coals having a carbon content of not more than 8'7 percent (calculated on the dry mineralfree coal as described in Technical Data on Fuel, published by the British National Committee, World Power Conference, 1950 edition, pages 394-395), and especially bright coals. In general the dull coals yield less extract than the bright coals. Especially high extractions are obtained with coals especially the bright coals, having a carbon content of not more than 83 per cent. (calculated on the same basis). Thus, for example, when a coal of the latter type is extracted with ethylene diamine at the boiling point for a period of 48 hours 35-40 per cent. of the coal substance can be extracted, but even for shorter periods of about 5 hours useful extractions are obtainable. The suitability of the extract for preparing aqueous dispersions decreases as the rank of the coal increases, but, when extracted with ethylene diamine, coals having a carbon content of not more than 87 per cent. generally yield extracts suitable for this purpose.

In order to facilitate the extraction it may be desirable to disintegrate the coal, advantageously to pass a 72 B. S. S. mesh sieve. Disintegration may be facilitated by softening the coal with the amine solvent.

The extraction process may be carried out advantageously with agitation, at the boiling point of the amine in an extraction apparatus of known type. Alternatively, it may be carried out at any temperature ranging from the melting point of the amine to the boiling point thereof. Thus, for example, the extraction may be conducted at a temperature not exceeding about 40 C., for example, at room temperature. The quantity of extract obtained at room temperature is' always less than that obtained at the boiling point under otherwise similar conditions. The quantity of extract can be increased, not only by working at a higher temperature, but also by subjecting the coal to successive extractions. For example, with four extractions of 1 hour each at room temperature with ethylene diamine the yields obtained were about one half of the yield mentioned above when working at the boiling point.

The invention also includes the production of a. coal extract by isolating theextract from the defined has been used,

organic --salt, for example,

' which has been isolated extract solution by treating the solution with a precipitating agent or by subjecting the solution to evaporation to remove the amine solvent therefrom. In this manner a carbonaceous material of low ash content is obtained. It has been possible to obtain material containing, for example, 0.1 to 0.6 per cent. of ash calculated on the weight of the dry material.

The precipitation may be means of an acid, the quantity sufiicient to combine with the whole or a part of the amine. Prior to-the addition'of the acid it is of advantage to dilute theextract'solution with water, in order sipation of the heat generated and to improvethe conditions of precipitation and the nature of the precipitate. Such preliminary dilution with water is, however, only possible when certain water-miscible amines have been used, that is'to brought about by say, aliphaticprimary amines which, in the case 'of monamines, contain not more than 4'carbon "atoms. The expression water-miscible amine is used'hereinafter and in the-appended claims to denote such'a primary aliphatic amine.

Alternatively, there may be used as a precipitating-agent an organic liquid'in which the coal eXtIactis at least-partially insoluble and which is miscible with the amine present in the extract solution. As such liquids there may be mentioned, benzene, carbon tetrachlorida'chldroform and ethy1 alcohol. After separating the precipitate, the precipitating solvent can generally be recovered from'the'mother liquor b'y'fractional distillation, "audit is of advantage so to select the amine solvent'andthe precipitating liquid that such recovery of the latter liquid is facilitated. Although "with many of these precipitatin'g liquids the wholeof the coal extract isnot'precipitated fromthe extract solution, the

amine solvent which remains after the recovery ofthe precipitating liquid'byfractional distillation, and which contains theunprecipitated'po-rtion of thecoal extract, can be reused a the amine solvent in a further coal extraction process. *tion of the precipitating -liquid froin the amine solvent should be sufilciently thorough to avoid impairing the solvent power of the amine solvent by "contamination with precipitating liquid. A'nother"method elf-precipitating the'coal ex- -tract, when a water-miscible amine solvent 'as is first :to dilute the extract solution with water and then coagulate 'it'by' the addition of-an' electrolyte such as an inmagnesium sulphate. 'Asfhowever, the coal extract tends to adsorb the added-salt, this method maybe less desirable if it-is-necessaryto keep the ash content of the coal extract-as low as possible.

The invention alsoincludescoal extract solutions obtained by the extraction process described above, and of which -'the concentration may have been adjustedbytheremoval or addition'ofamine solvent; and also includes coal 'extract solutions obtained by dissolving in an amine of the kind hereinbefore referred to a coal extract in the manner described above.

Ihe invention further includes aqueous dispersions which have been obtainedbydispersing water 'a coalextract -solution, which has'been obtair-iedas described in the preceding paragraph, and which contains as 'the solvent a watermiscible amineas defined above.

'll he coal extract solutions or aqueous-disperacid being added in a to secure a better 'dis- I-t will'be understood that the-separasions can be used for various purposes, and especially as coating compositions for providing prolution or aqueous =Of solutions 01 tective coatings on the surfacesfor example, of metal, ceramic "or glass materials or articles. Accordingly, the invention also includes a method or coating surfaces, in which the coal extract solution or aqueous dispersion is applied to the surface, for example, by brushing, dipping or spraying, and the coating is baked at a temperature of about 250-300" C. If the extract sodispersion is applied directly at 'ahigh concentration there may be a tendency for the coating "-to'shrink and crack during baking and ultimately to break away. However, concentrations ranging from 2 to 6 grams of extract per 10060; of the solution or dispersion have been found to give satisfactory coatings. In the case dispersions of low concentration and consequent low viscosity, such as those last mentioneditis of advantage to assist the spreading 'of "the'liquid on the-surface'by heating the surface so as to cause'evaporation to set in "im- -mediately onapplyingthe liquid to the surface.

Coatings produced as described above are hard, Wate'r repellent and substantially insoluble in organic li'quids'and water. Owing to their water- 'repellent :character the coatings are not wetted by"water. By virtue of this property the-coati'rig compositions are especially suitable for application to steam condensers 'on the surface thereof on which condensation 'occurs, for example, on the steam'side of condenser 'tubes. The steam condenses on the-coated surface 'in the form of droplets, whereby heat 'transfer is enhanced. "It has 'beenfound that=hardcoatings of especially high insolubility 'in organic liquids are obtained when "the amine solvent in the extract solution or aqueous dispersion is monoethanolamine or an alkylene diamine, for

example, ethylene 'di'amine or hexamethylene diamine. In' the 'case of"aqueousdispersions, those which havebeenprepa'red' by diluting an extract solution'with too large a quantity of water, tend to lead to theformation of porous coatings. It'is therefore generally desirableto use for dilution a tion. In these examples the following coals were used:

Percentage content v V Volatile Coal Description 0 (by matter, a

C 'H N idifieronce) A"... Free-burningNo'rth- 81.8 sis 118 11.1 37.4

umberland. B Yorkshire 84;5 5.4 1.9 --8 .2 35.6 C North Stafiordshire, 86.3 5.3 2.2 6.2 32.9 f

1 Calculated on the dry mineral-free coal as"des'cribe'd in TechnicalData on Fuel, see-above.

2 Calculated on the dry mineral-free; coal determined on Parrs basis as described in American Society for Testing Materials Standards, 1949, Part5, Specification D388e-38,

page 656.

The above "coals were all bright coals.

Example '1 The amine solvents and -coals indicated in thetablej given below-were used. .Quantitiesvarying' from 2-10 gramsfiof the different coals, each dried and groundto --passa -72 B. S. S. -mesh sieve, *were extractedwith =.quantities of the -various solvents exceeding the stated minimum volumes required-to ensure that a maximum extraction was obtained in eachcase. For each extraction the coal sample was placed in a glass tube of about 100 cc. capacity, having a stopcock at its lower end and a removable stopper in its upper open end, and provided with a filter of porous sintered glass near its lower end. The appropriate volume of solvent was added, and the tube was shaken at room temperature for 1 hours, although a considerably shorter period of about 15 minutes would in most cases suffice to secure a maximum extraction. The coal extract solution was then withdrawn by suction leaving the residual coal upon the filter.

The quantity of coal extract in the solution was determined by precipitating the extract by means of hydrochloric acid, separating the precipitate by filtration, washing the precipitate with water, drying it, and weighing the dried material. The quantities of extract are ex' pressed as a percentage of the coal used (calculated as dry mineral free coal). Since the extracts contained traces of hydrogen chloride and solvent, which could not be removed by the washing, a correction factor (found to be approximately constant by numerous preliminary tests) to allow for these impurities was used in arriving at the percentages of extract.

In the case in which four extractions were used, the coal sample was extracted four times in succession with fresh quantities of the solvent and the weight of coal extract from the combined extract solutions was determined.

Repetition of the above extractions with quantities of coal and solvents ten times larger gave identical results.

Example 2 The amine solvents and coals indicated in the table given below were used. Quantities of about 15 grams of the diiferent coals, each dried and ground to pass a 72 B. S. S. mesh sieve, were extracted with about 250 cc. of the various solvents at the boil in a Soxhlet apparatus for a period of 48 hours. The quantities of coal extract obtained were determined and calculated as described in Example 1.

Percentage ex rec Solvent Coal on the coal used Ethylene diamine A 38.6

Do B 31.4

In the particular experiments described in this example a period of 48 hours was used to ensure that the extraction should be as far as possible complete, but it is possible in extractions at the boil with considerably shorter periods of 5-7 hours to obtain quantities of extract of the order of per cent of those given above.

Emample 3 96 cc. of a coal extract solution, prepared from coal A by extraction with ethylene diamine at room temperature in a manner similar to that described in Example 1, and containing 1.26 grams of extract per 100 cc. of extract solution, were mixed with 288 cc. of carbon tetrachloride in order to precipitate a part of the extract. The precipitate, which rose to the top of the liquid, was separated, washed four times with 24 cc. of fresh carbon tetrachloride on each occasion, and then allowed to dry in the atmosphere. The product was then in the form of hard glossy lumps.

The combined filtrate and washings were then subjected to fractional distillation at 20-30. C. under reduced pressure in order to recover the carbon tetrachloride. The use of reduced pressure was necessary in order to avoid chemical reaction between the two solvents. 384 cc. of carbon tetrachloride were distilled together with a little ethylene diamine. The distillation residue, amounting to 81 cc., had the appearance and properties of an extract solution of coal in ethylene diamine, and contained 0.98 gram of coal extract per 100 cc. of solution.

The distillation residue was used as the solvent in an extraction process carried out at room temperature in the manner described in Example 1. The resulting extract solution contained 4.6 grams of coal extract per 100 cc. of solution, which was somewhat higher than the concentration of the extract solution obtained by extracting the coal in the same manner with fresh ethyl- Example 4 79 cc. of a coal extract solution, prepared from coal A by extraction with monoethanolamine at the boil in a manner similar to that described in Example 2, and containing 2.7 grams of extract per 100 cc. of solution, were mixed with 1500 cc. of ethyl alcohol in order to precipitate a part of the extract. The precipitate, which sank to the bottom of the liquid, was separated by filtration, washed five times with 63 cc. of fresh ethyl alcohol on each occasion, and then allowed to dry in the atmosphere.

The combined filtrate and washings were then subjected to distillation under atmospheric pressure with a moderate degree of fractionation until all the alcohol had distilled. The distillation residue, amounting to 75 cc., resembled'an extract solution of coal in monoethanolamine, and contained 0.84 gram of coal extract per 100 cc. of solution.

The distillation residue was used as a solvent in an extraction process carried out at room temperature in the manner described in Example 1. Comparison with the result of the same extraction carried out with fresh monoethanolamine containing the same amount of coal extract showed that the solvent power of the recovered monoethanolamine was not impaired. V

Example Brass tubes and glass slides were coated; some with (a) a coal extract solution prepared from coal A by extraction with ethylene diamine at room temperature as described in Example 1, and

containing 2.7 grams of extract per 100 cc. of solution, and others with (b) a coal extract solution prepared from coal A by extraction with monoethanolamine at the boil as described in Example 2, and containing 2.7 grams of extract per 100 cc; of solution. Owing to the low viscosity of these solutions, the surfaces to which they were applied were heated to about the boiling point of the solvent. The coatings were then baked by heating them slowly up to a temperature' of 250-300 C. and maintaining them at that temperature for about s; hour. The baked coatings adhered strongly to the surfaces, and were glossy, hard and could not be wetted by water.

The coal extract solution (b) was concentrated to a content of extract amounting to 5.8 grams per 100 cc. of solution. The viscosity was still somewhat low for satisfactory application to cold surfaces. The concentrated solution was applied and baked in the manner described in the preceding paragraph. Good coatings were obtained, but were not quite so glossy as those produced with the less concentrated solutions.

Example 6 A coating of the coal extract solution (b) described in the first paragraph of Example 5 was applied to the exterior of a heated glass cylinder and baked in the manner described in that example at 270 C. The glass cylinder was then fitted; so as to form a reflux condenser cooled by the flow of water through its interior, in an apparatus in which distilled water was boiled and refluxed continuously. The steam condensed in the form of droplets on' the coated exterior of the glass cylinder, and continued to do so over a period of 56 days. As could be seen from the lack of colour in the water none of the coating hadbe'en removed.

I claim:

1. A method of coating surfaces, which comprises extracting ahitumino'us coal with a liquid amine selected from the group consisting ofliquidaliphatic and araliphatic amines containing at least one primary amino group, and havingLa viscosity not greater than'30 centipoises at the extraction temperature, under atmospheric'pres sure and at a temperature not higher than the boiling point of the amine; coating the surface with a solution of the coal extract in such" an amine, and-baking the coatingon the surface at atemperature of about 250-300 C;

2. A method as claimed in claim 1, wherein the amine is a primary aliphatic monamine containing not more than 12 carbon atoms.

3. Amethod as claimed in claim 2, wherein the amine is selected from the group consisting of npropylamine, isopropylamine, a-methyl-propylamine, n-amylamine, n-dodecylamirie, allylamine and mono-ethanolamine. H

4. A method as claimed in claim 1, wherein the amine is an alkylene diamine containing not more tha 6 carbon atoms in the aliphatic chain;

5. A method as claimed in claim 4, wherein the iidaiiitt alkylen'e diamine is selected rom the? "g ad sisting of ethylene diamine, propylene diamine and hexamethylene diamine. I H M 6. A method as claimed in claim 1, wherein the airline is a polyalkylenfe polyamine. W N 7. A method as claimed in claimfi; whereinthe 11. A method as climed in claim 1, wherein the coal treated is a bright coal having a carbon content of notmore than 83 per cent. calculated as described in Technical Data on Fuel, pubmass by the British National Committee, World Power Conference, 1950 edition, pages 394-395.

12. A method as claimed in claim 1, wherein the amine solution er the coal extract is coated on the surface with a concenltrationrang ing' from 2 to 6 grams of extract per cc. of the solution.

13. A method as claimed in claim 1, wherein the amine of the solution of the coal extraet is a water-miscible amine and the solultion is coated on the surface in the form of an aqueous dispersion of the solution.

14. A method as clairried in claim 13, wherein the aqueous dispersion is coated on the surface with a concentration ranging from 2 to 6 grams of extract per 100 cc. of lthe dispersion.

15. A method as claimed in claim 13, wherein the aqueous dispersion contains a' volume of we ter not greater than the volume of the dispersed solution of the extract. ....l.. I eihQ9.9 seat. a s l ate hprises extracting a, bituminous coal with ethylene diamine under atmospheric pressure and at a temperature not higher than the boiling point of the amine, coating the surface with the extract solution with a concentration ranging from 2 to 6 grams of extract per 100 cc. of the solution, and baking the coating on the surface at a temperature of about 250-300 C.

1'7. A method of coating surfaces-which corriprises extracting a bituminous coal with monoethanolamine under atmospheric pressure and at a temperature not higher than the boiling point of the amine, coalting'the surface with the extract solution with a concentration ranging from 2' t0 6 g amsof extract per l0 0 cc. of the solution, and hat ng the coating n the surface at a temperature of about 25013009 C.

IAN GORDON cut MING DRYDEN.

OTHER Abraham, Asphalts an Aiiied substances; 5 th ed. (1945);!)1 884-887. 

1. A METHOD OF COATING SURFACES, WHICH COMPRISES EXTRACTING A BITUMINOUS COAL WITH A LIQUID AMINE SELECTED FROM THE GROUP CONSISTING OF LIQUID ALIPHATIC AND ARALIPHATIC AMINES CONTAINING AT LEAST ONE PRIMARY AMINO GROUP, AND HAVING A VISCOSITY NOT GREATER THAN 30 CENTIPOISES AT THE EXTRACTION TEMPERATURE, UNDER ATMOSPHERIC PRESSURE AND AT A TEMPERATURE NOT HIGHER THAN THE BOILING POINT OF THE AMINE, COATING THE SURFACE WITH A SOLUTION OF COAL EXTRACT IN SUCH AN AMINE, AND BAKING THE COATING ON THE SURFACE AT A TEMPERATURE OF ABOUT 250-300* C. 